September 26, 2013

Tuberculosis and Out of Africa

Nature Genetics 45, 1176–1182 (2013) doi:10.1038/ng.2744

Out-of-Africa migration and Neolithic coexpansion of Mycobacterium tuberculosis with modern humans

Iñaki Comas et al.

Tuberculosis caused 20% of all human deaths in the Western world between the seventeenth and nineteenth centuries and remains a cause of high mortality in developing countries. In analogy to other crowd diseases, the origin of human tuberculosis has been associated with the Neolithic Demographic Transition, but recent studies point to a much earlier origin. We analyzed the whole genomes of 259 M. tuberculosis complex (MTBC) strains and used this data set to characterize global diversity and to reconstruct the evolutionary history of this pathogen. Coalescent analyses indicate that MTBC emerged about 70,000 years ago, accompanied migrations of anatomically modern humans out of Africa and expanded as a consequence of increases in human population density during the Neolithic period. This long coevolutionary history is consistent with MTBC displaying characteristics indicative of adaptation to both low and high host densities.

2 comments:

Yeah, I saw that paper when it came out (I think it was linked to from BBC). It's pretty neat, especially the aligning of the trees with mtDNA and the fact that it supports two ooA (lineage 1 versus 2, 3, and 4) and plenty back-migration into Africa.

Of course I don't agree with their ages - their timing arguments are circular and rely on mtDNA L3 estimates and the presupposition that ooA was ~70,000 ya. However, if you multiply everything by ~1.6, then the first ooA occurs around ~110,000 ya, and "Europe" (In reality Europe, Americas, and Africa) and East and Central Asia (again, also Africa) split around Toba.

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